An optical network can be broadly considered as one that includes nodes that accept, output, and/or redirect information channels (packets, or circuits), and transport facilities, for example, optical cables, that interconnect the nodes. The cable between nodes of a network may comprise only one fiber, or may have a large number of fibers.
FIG. 1 illustrates a segment of an optical network encompassing Chicago having a traffic element (TE) 101, Indianapolis having a traffic element 102, Pittsburgh having a traffic element 103, New York having a traffic element 104, Atlanta having a traffic element 105, and Philadelphia having a traffic element 106. It is noted that a cable between two cities need not consist of an uninterrupted span. For example, the cable from Indianapolis is shown to comprise a section from Indianapolis to a junction element, and another section from the junction element to Pittsburgh. A similar arrangement is shown for the span between Philadelphia (Phili) and New York city (NYC) and for the span between Atlanta and Phili. Although a junction element is not required for adding, or off-loading traffic, it is possible to change wavelengths within it and, therefore, a signal of a particular wavelength that flows through one section does not absolutely have to continue through the other segment in the same wavelength. It may be noted that in the context of this disclosure, the term “wavelength” means a signal that results when information is modulated onto an optical carrier that is relative pure; i.e., has a very narrow bandwidth. Signals of other wavelengths are separated sufficiently apart so that each wavelength can be culled out, if desired.
Currently, the process for establishing traffic carrying capacity between a pair of points contemplates simply managing the physical cable connections at the points, including intermediate junctions. Thus, in order to establish capacity between Chicago and Indianapolis, a cable needs to be physically connected that extends to the intended destination. FIG. 2 illustrates a traffic element that illustratively is used in Phili. Specifically, the traffic element 106 comprises an optical add/drop multiplexer (OADM) 116, and the cables from Pittsburgh, Atlanta, and NYC are connected to the OADM.
Router 126 is poised to place traffic onto the network, or to receive traffic from the network. Currently, in order to provision capacity from element 106 to any particular direction, for example, to NYC, circuitry must be provided at element 106 that converts electrical signals, and/or short-reach optical signals, to long-reach optical signals at a particular wavelength, and the developed optical signal must be coupled to the cable extending to NYC, for example with a coupler as shown in FIG. 2. To change the provisioning from NYC to, for example, Atlanta, the coupling had to physically be changed to couple the output signal of router 126 to the Atlanta cable, and the wavelength at which the signals are operating may have to be changed. Of course, capacity can be provided ab initio to all of the destinations, as shown in FIG. 2, but that is very expensive.